Is there an equivalent grade to S355K2G1W in the BS 4360 standard

If you're working with an old specification or maintaining a legacy structure, you might encounter BS 4360 grade designations. The question comes up often: does this retired British standard have a direct match for modern EN 10025-5's S355K2G1W?

The short answer: Yes – WR50D is your closest match.

Technical cross-reference tables show that S355K2G1W (under its previous EN 10155 designation) corresponds to WR50D in BS 4360:1990 .

Why WR50D?

The weathering steel family under BS 4360 used the "WR" prefix (Weather Resistant). The numbering followed a similar logic to the EN grades:

WR50 series = 355 MPa minimum yield strength (matching the "355" in S355K2G1W)

Suffix D = indicates low-temperature impact testing



While S355K2G1W guarantees 27J at -20°C (with no individual test below 20J), WR50D historically specified a minimum of 40J at -20°C . This means WR50D is actually a higher-toughness specification—so if you're substituting, the British grade meets or exceeds the European requirement. However, always verify the specific test values on the mill certificate, as older standards had different sampling rules.

A note on chemistry (G1W vs. standard WR50D).

The "G1" in S355K2G1W indicates lower phosphorus (≤0.035%) for improved weldability and consistent impact properties. BS 4360 WR50D typically allowed slightly higher phosphorus. For most structural applications, this difference is minor. But if your welding procedure is sensitive or the specification explicitly calls out G1 chemistry, request a chemical analysis from the supplier.

What about the old corrosion-resistant grades?

BS 4360 also specified WR50C, which is more common in commercial references but tests at 0°C—not cold enough if you need -20°C performance . For true low-temperature weathering steel matching S355K2G1W, WR50D is the correct target.

Practical takeaway for today's buyer.

Since BS 4360 was withdrawn and replaced by EN 10025 in the early 2000s, you won't find mills producing new material to WR50D. But if you're replacing a component in an old bridge or cross-referencing for material traceability, understand that:

S355K2G1W (current EN standard) can replace WR50D – with equal or better impact properties

WR50D in old records is equivalent to S355K2G1W – for maintenance and requalification purposes

When in doubt, request a current EN 10025-5 certification with the same thickness and impact requirements. That's the safest path forward.